If Iowa caucus polls were like sweepstakes, Michele Bachmann would have just opened the door to Ed McMahon and a huge bunch of balloons. Tim Pawlenty‘s the neighbor who bought 100 magazine subscriptions, only to see the celebration going on next door.

Bachmann is riding high in the first Des Moines Register Iowa Poll of likely GOP caucusgoers. She’s just one percentage point behind Mitt Romney, the national front-runner, in an eight-person field. The Minnesota congresswoman is by far the most popular out of 18 current or potential candidates, including Sarah Palin. All on the eve of her formal presidential campaign launch.

Pawlenty has invested heavily in Iowa. He’s spent 26 days in the state since November 2009, has an A-list Iowa staff, has done a direct-mail piece and was on TV with an ad on the last night of polling. The former Minnesota governor done everything a caucus candidate is supposed to do. And he’s not any better off in the poll than Newt Gingrich, whose campaign is in ashes. It hardly seems fair.

Bachmann was a standout in the June 13 debate in New Hampshire, while Pawlenty was panned for failing to press his earlier attacks on Romney’s health-care record. But that’s not enough to account for such a wide gulf in popularity.

Register pollster J. Ann Selzer says Bachmann is a good fit for Iowa, at least on paper. She’s an Iowa native, born in Waterloo. She checks all the boxes for conservative issues and has a national platform with the tea party. She can raise a lot of money. And, not inconsiderably, she’s fresh and dynamic.

Pawlenty has also been seen as a good match for Iowans. He’s likable — his net favorability numbers are second only to Bachmann’s at 45 points. He has worked to position himself as a candidate for all types of Republicans — saying what religious conservatives want to hear while touting his fiscal record for the business-oriented set. Maybe he’s tried too hard to please everyone.

More likely, Pawlenty’s problem is that his early and aggressive organization has earned him an extra helping of scrutiny and criticism. Democrats and sympathizers have been trashing his Minnesota budget and tax record for months. His economic plan, which included a highly optimistic 5 percent growth rate, has met with incredulous media reviews.

Bachmann has not faced anything comparable. She has a reputation for gaffes and factual flubs and is light on congressional accomplishments, but she has seen nothing yet in the way of organized attacks on her record. She has not put forth detailed proposals for a Bachmann presidency. That will come, and whether she has lasting star power or just a vapor trail will depend on how well she handles the heat.

Romney’s numbers can spin in either direction. That he’s only one percentage point ahead of an upstart like Bachmann might suggest he was right to steer clear of Iowa. On the other hand, that he still leads the pack after spending only a single day in Iowa this cycle means he has a very loyal base. It is hard to imagine Romney gaining more support, however, without coming to Iowa to ask for it.

Pawlenty has been seen as Romney’s chief competitor for mainstream Republicans. But the Minnesotan has not capitalized much on Romney’s absence from Iowa — only 15 percent of Romney supporters even include Pawlenty as a second choice.

As for the rest of the field:

Herman Cain: Third place is an excellent position for Cain, who is still introducing himself to caucusgoers. At 10 percent, he’s the only candidate besides Romney and Bachmann in double digits.

Gingrich: Only gay-activist Fred Karger has higher unfavorable ratings among declared GOP candidates. If the former U.S. House speaker was looking to Iowa to resurrect his smoldering campaign, his finish in this poll behind Romney, Bachmann, Cain and “not sure” should be sobering.

Ron Paul: The Texas congressman had nearly 10 percent of the vote on caucus night in 2008, in fifth place. He’s tied for fourth with Gingrich in this poll, although his favorability ratings are far more positive. He has a chance to move up.

Rick Santorum: He’s lagging behind the field at 4 percent, despite spending significant time in Iowa. He’s still not well-known, with 45 percent of caucusgoers not sure what they think of him. And he’s facing stiff competition for the religious-conservative vote.

Potential candidates: Fourteen percent of likely caucusgoers are undecided, and 69 percent say they could be persuaded to support someone else. There’s still ample opportunity for a candidate like Texas Gov. Rick Perry (43 percent favorable, 8 percent unfavorable) to jump in. Palin is still popular, with a stronger net favorability rating than Romney.

The field may not be set, and neither are the fates sealed for candidates who are struggling. In May 2007, the Iowa Poll had eventual caucus-winner Mike Huckabee with 4 percent, tied with U.S. Rep. Tom Tancredo of Colorado. There’s still plenty of time for someone to burst the front-runners’ balloon.